This invention relates to thermometers for humans and more particularly to a thermometer which is safe, accurate, relatively easy to manufacture and capable of being manufactured in mass production numbers.
In recent years the use of glass mercury thermometers has been questioned because such thermometers are expensive to manufacture, present a potential breakage problem and usually are not economically disposable.
Glass thermometers also present a problem of sterilization which of course, is highly desirable if they are to be reused particularly by other patients. If the thermometers are not properly sterilized after use there is a danger of transmission of infectious diseases by cross-contamination.
Typically, in glass thermometers mercury has been used as the temperature indicating substance in the thermometer because of certain of mercury's physical characteristics which enable it to indicate the patient's temperature even long after removal from the patient. The use of mercury, however, creates potential health hazards in the event of thermometer breakage while in use.
The use of mercury as the temperature indicating fluid creates toxicity problems during the manufacturing process. The calibration of glass thermometers traditionally has been a time consuming process not easily adaptable to automation and masss production.
Nevertheless, despite certain shortcomings of glass thermometers they remain the most popular of the devices for determining the temperature of human beings. Also the use of mercury continues to be the most widely used temperature indicating fluid.
Attempts from time to time have been made to produce disposable thermometers using materials such as plastic and using liquids other than mercury as the temperature indicating liquid but such attempts have been largely not satisfying because of inaccuracy, expense, manufacturing complexities and inability to obtain temperature retention qualities after removal from the patient. In other words where liquids other than mercury have been used as the temperature indicating liquid it has been necessary to read the thermometer while it is in the patient or an inaccurate reading will be obtained.
An additional problem has been to prevent premature recording of temperature due to elevated storage temperature prior to use by patient. Warehouse temperatures, for example, can be significantly higher than human temperatures.